The present invention relates to an image processing system, projector, program, information storage medium and image processing method which can correct the distortion of an image and also adjust a focus.
An image projected from an image display device such as a projector may be distorted to create a so-called keystone distortion in the vertical or horizontal direction, depending on the relationship between the image display device and a position onto which the image is projected therefrom. Even if the image display device is placed substantially correctly relative to an object to be projected, the image may be defocused when the distance between the image display device and the object to be projected varies.
Thus, the image display device must display an image with no image distortion or defocusing.
In a general projector with functions of image distortion correction and auto-focus, however, a user semi-automatically corrects the distortion in an image by indicating four corners in a screen by the use of a mouse or the like. Additionally, to perform the auto-focusing function in the general projector, calibration images have been projected after the correction of image distortion has been released once. In this case, if the projector again corrects the image distortion, the corrected projection area cannot be adequately focused.
It is troublesome for the user to indicate the four corners in the screen using the mouse or the like.
To overcome such a problem, for example, Japanese Patent Laid-Open No. 2000-241874 has proposed an automatic screen-position adjusting apparatus for projector which includes a projection lens capable of adjusting the focus, zooming, elevation angle and tilt angle, a monitor camera located on the forward face of the main projector body for sensing an image projected onto a screen, data conversion means for converting information of image signals inputted from the monitor camera into digital data and storing the converted digital data, computation means for computing the converted digital data from the data conversion means, means for adjusting the focus of the projection lens, zooming drive means for zooming the projection lens, means for detecting the position of the screen within the sensed by the monitor camera, and means for adjusting the keystone distortion in the projected image based on the data of the detected screen position.
However, the technique of Japanese Patent Laid-Open No. 2000-241874, is to project and sense a test pattern image to detect the best focus, to adjust the focus, to project and sense an all-white image to detect endpoint nodes on a screen, to reduce or magnify a projection range until the projected image reaches the endpoint nodes of the screen by zooming, and to adjust the orientation of the forward face of the main projector body or angles of depression and elevation so that the projected image is located in the center of the screen.
This technique further examines and adjusts the keystone distortion by comparing the lengths of the opposed sides of the screen within the sensed image with each other.
The technique of Japanese Patent Laid-Open No. 2000-241874 cannot possibly provide the best focus originally intended by the user in the keystone-distorted image since it corrects the keystone distortion after the focus has been adjusted once as described.
Moreover, the detection of the screen position requires a high-resolution camera, resulting in increase of the manufacturing cost.
The technique of Japanese Patent Laid-Open No. 2000-241874 further adjusts the angles of depression and elevation in the main projector body so that the image is forcedly projected in the center of the screen taking no account of the original image projecting position. Such a process premises that the main projector body is located substantially in direct front of the screen.
In fact, however, a laterally keystone distortion occurs if the main projector body is not located substantially in direct front of the screen. If the process is made presuming that the main projector body is located substantially in direct front of the screen, thus, the laterally keystone distortion cannot properly be corrected.
An image intended by the user cannot be displayed if the angles of depression and elevation in the main projector body are adjusted so that the image is forcedly projected in the center of the screen taking no account of the projecting position intended by the user. More particularly, it is conceivable that the user may project an image on the screen only at its right half since there is an obstacle in front of the central screen location.